Expandable liquid volume in an led bulb

ABSTRACT

An LED bulb includes a shell, one or more LEDs, a thermally conductive liquid, and a liquid-volume compensator mechanism. The one or more LEDs are disposed within the shell. The thermally conductive liquid is held within the shell. The liquid-volume compensator mechanism is configured to compensate for expansion of the thermally conductive liquid.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 13/631,660, filed Sep. 28, 2012, issued as U.S. Pat. No.8,562,185 on Oct. 22, 2013, which is a Continuation of U.S. patentapplication Ser. No. 13/419,373, filed Mar. 13, 2012, issued as U.S.Pat. No. 8,277,094 on Oct. 2, 2012, which is a Continuation of U.S.patent application Ser. No. 13/021,639, filed Feb. 4, 2011, issued asU.S. Pat. No. 8,152,341 on Apr. 10, 2012, which are incorporated herebyby reference in their entirety for all purposes.

BACKGROUND

1. Field

The present disclosure relates generally to liquid-cooled light-emittingdiode (LED) bulbs and, more specifically, to providing an expandablevolume in an LED bulb to allow for thermal expansion of a thermallyconductive liquid.

2. Related Art

Traditionally, lighting has been generated using fluorescent andincandescent light bulbs. While both types of light bulbs have beenreliably used, each suffers from certain drawbacks. For instance,incandescent bulbs tend to be inefficient, using only 2-3% of theirpower to produce light, while the remaining 97-98% of their power islost as heat. Fluorescent bulbs, while more efficient than incandescentbulbs, do not produce the same warm light as that generated byincandescent bulbs. Additionally, there are health and environmentalconcerns regarding the mercury contained in fluorescent bulbs.

Thus, an alternative light source is desired. One such alternative is abulb utilizing an LED. An LED comprises a semiconductor junction thatemits light due to an electrical current flowing through the junction.Compared to a traditional incandescent bulb, an LED bulb is capable ofproducing more light using the same amount of power. Additionally, theoperational life of an LED bulb is orders of magnitude longer than thatof an incandescent bulb, for example, 10,000-100,000 hours as opposed to1,000-2,000 hours.

While there are many advantages to using an LED bulb rather than anincandescent or fluorescent bulb, LEDs have a number of drawbacks thathave prevented them from being as widely adopted as incandescent andfluorescent replacements. One drawback is that an LED, being asemiconductor, generally cannot be allowed to get hotter thanapproximately 120° C. As an example, A-type LED bulbs have been limitedto very low power (i.e., less than approximately 8 W), producinginsufficient illumination for incandescent or fluorescent replacements.

One potential solution to this problem is to use a large metallic heatsink attached to the LEDs and extending away from the bulb. However,this solution is undesirable because of the common perception thatcustomers will not use a bulb that is shaped radically different fromthe traditionally shaped A-type form factor bulb. Additionally, the heatsink may make it difficult for the LED bulb to fit into pre-existingfixtures.

Another solution is to fill the bulb with a thermally conductive liquidto transfer heat from the LED to the shell of the bulb. The heat maythen be transferred from the shell out into the air surrounding thebulb. As heat is transferred from the LED to the conductive liquid, thetemperature of the liquid increases, resulting in an increase in theliquid volume due to thermal expansion. Some liquid-filled LED bulbs usea pocket of air or bubble in the bulb. As the temperature of the liquidincreases, the volume of the liquid expands, and the pocket of air orbubble is compressed.

However, it is undesirable to have a pocket of air or bubble in theliquid-filled bulb. First, a pocket of air reduces the coolingefficiency of the bulb by creating an air barrier between the liquid andat least a portion of the outer shell housing. Second, the bubble maydistort the light created by the LED, resulting in a non-uniform lightdistribution. The bubble may create a bright reflection or darkened areadetracting from the visual appeal of the bulb. Third, an air bubbledraws attention to the fact that the bulb is filled with a liquid, whichmay not be appealing to customers.

SUMMARY

In one exemplary embodiment, an LED bulb includes a base, a shellconnected to the base, one or more LEDs, a thermally conductive liquid,and a flexible diaphragm. The one or more LEDs are disposed within theshell. The thermally conductive liquid is held within the shell. Theflexible diaphragm is in fluidic connection to the thermally conductiveliquid, and is configured to deflect from a first position to a secondposition to compensate for expansion of the thermally conductive liquid.

DESCRIPTION OF THE FIGURES

FIG. 1 depicts a cross-sectional view of an LED bulb with a diaphragm.

FIG. 2A depicts a cross-sectional view of an LED bulb with a diaphragmand piston in extended position.

FIG. 2B depicts a cross-sectional view of an LED bulb with a diaphragmand piston in retracted position.

FIG. 3A depicts a cross-sectional view of an LED bulb with a diaphragm,piston, and return spring in extended position.

FIG. 3B depicts a cross-sectional view of an LED bulb with a diaphragm,piston, and return spring in retracted position.

FIG. 4A depicts a cross-sectional view of an LED bulb with a shroudeddiaphragm, piston, return spring, and inverted rod in extended position.

FIG. 4B depicts a cross-sectional view of an LED bulb with a shroudeddiaphragm, piston, return spring, and inverted rod in retractedposition.

FIG. 5A depicts a cross-sectional view of an LED bulb with a shroudeddiaphragm, piston, and inverted rod in extended position.

FIG. 5B depicts a cross-sectional view of an LED bulb with a shroudeddiaphragm, piston, and inverted rod in retracted position.

DETAILED DESCRIPTION

The following description is presented to enable a person of ordinaryskill in the art to make and use the various embodiments. Descriptionsof specific devices, techniques, and applications are provided only asexamples. Various modifications to the examples described herein will bereadily apparent to those of ordinary skill in the art, and the generalprinciples defined herein may be applied to other examples andapplications without departing from the spirit and scope of the variousembodiments. Thus, the various embodiments are not intended to belimited to the examples described herein and shown, but are to beaccorded the scope consistent with the claims.

Various embodiments are described below, relating to LED bulbs. As usedherein, an “LED bulb” refers to any light-generating device (e.g., alamp) in which at least one LED is used to generate the light. Thus, asused herein, an “LED bulb” does not include a light-generating device inwhich a filament is used to generate the light, such as a conventionalincandescent light bulb. It should be recognized that the LED bulb mayhave various shapes in addition to the bulb-like A-type shape of aconventional incandescent light bulb. For example, the bulb may have atubular shape, globe shape, or the like. The LED bulb of the presentdisclosure may further include any type of connector; for example, ascrew-in base, a dual-prong connector, a standard two- or three-prongwall outlet plug, bayonet base, Edison Screw base, single pin base,multiple pin base, recessed base, flanged base, grooved base, side base,or the like.

As used herein, the term “liquid” refers to a substance capable offlowing. Also, the substance used as the thermally conductive liquid isa liquid or at the liquid state within, at least, the operating ambienttemperature range of the bulb. An exemplary temperature range includestemperatures between −40° C. to +40° C. Also, as used herein, “passiveconvective flow” refers to the circulation of a liquid without the aidof a fan or other mechanical devices driving the flow of the thermallyconductive liquid.

FIG. 1 illustrates a cross-sectional view of an exemplary LED bulb 100.LED bulb 100 includes a base 110 and a shell 101 encasing the variouscomponents of LED bulb 100. For convenience, all examples provided inthe present disclosure describe and show LED bulb 100 being a standardA-type form factor bulb. However, as mentioned above, it should beappreciated that the present disclosure may be applied to LED bulbshaving any shape, such as a tubular bulb, globe-shaped bulb, or thelike.

Shell 101 may be made from any transparent or translucent material suchas plastic, glass, polycarbonate, or the like. Shell 101 may includedispersion material spread throughout the shell to disperse lightgenerated by LEDs 103. The dispersion material prevents LED bulb 100from appearing to have one or more point sources of light.

In some embodiments, LED bulb 100 may use 6 W or more of electricalpower to produce light equivalent to a 40 W incandescent bulb. In someembodiments, LED bulb 100 may use 20 W or more to produce lightequivalent to or greater than a 75 W incandescent bulb. Depending on theefficiency of the LED bulb 100, between 4 W and 16 W of heat energy maybe produced when the LED bulb 100 is illuminated.

The LED bulb 100 includes several components for dissipating the heatgenerated by LEDs 103. For example, as shown in FIG. 1, LED bulb 100includes one or more LED mounts 107 for holding LEDs 103. LED mounts 107may be made of any thermally conductive material, such as aluminum,copper, brass, magnesium, zinc, or the like. Since LED mounts 107 areformed of a thermally conductive material, heat generated by LEDs 103may be conductively transferred to LED mounts 107. Thus, LED mounts 107may act as a heat-sink or heat-spreader for LEDs 103.

LED mounts 107 are attached to bulb base 110, allowing the heatgenerated by LEDs 103 to be conducted to other portions of LED bulb 100.LED mounts 107 and bulb base 110 may be formed as one piece or multiplepieces. The bulb base 110 may also be made of a thermally conductivematerial and attached to LED mount 107 so that heat generated by LED 103is conducted into the bulb base 110 in an efficient manner. Bulb base110 is also attached to shell 101. Bulb base 110 can also thermallyconduct with shell 101.

Bulb base 110 also includes one or more components that provide thestructural features for mounting bulb shell 101 and LED mount 107.Components of the bulb base 110 include, for example, sealing gaskets,flanges, rings, adaptors, or the like. Bulb base 110 also includes aconnector base 115 for connecting the bulb to a power source or lightingfixture. Bulb base 110 can also include one or more die-cast parts.

LED bulb 100 is filled with thermally conductive liquid 111 fortransferring heat generated by LEDs 103 to shell 101. The thermallyconductive liquid 111 fills the enclosed volume defined between shell101 and bulb base 110, allowing the thermally conductive liquid 111 tothermally conduct with both the shell 101 and the bulb base 110. In someembodiments, the enclosed volume includes less than about 5 percent ofgas when filled with the thermally conductive liquid 111. In someembodiments, thermally conductive liquid 111 is in direct contact withLEDs 103.

Thermally conductive liquid 111 may be any thermally conductive liquid,mineral oil, silicone oil, glycols (PAGs), fluorocarbons, or othermaterial capable of flowing. It may be desirable to have the liquidchosen be a non-corrosive dielectric. Selecting such a liquid can reducethe likelihood that the liquid will cause electrical shorts and reducedamage done to the components of LED bulb 100.

LED bulb 100 includes a liquid-volume compensator mechanism tofacilitate thermal expansion of thermally conductive liquid 111contained in the LED bulb 100. In the exemplary embodiment depicted inFIG. 1, the liquid-volume compensator mechanism includes diaphragmelement 120 for providing an expandable liquid volume. Diaphragm element120 is a flexible membrane that is chemically compatible with thermallyconductive liquid 111. Diaphragm element 120 may be made of an elastomeror synthetic rubber, such as Viton. Other suitable materials includesilicone, fluorosilicone, fluorocarbon, Nitrile rubber, or the like.While the present embodiment of a liquid-volume compensator mechanismincludes a diaphragm element 120, one skilled in the art would recognizethat a liquid-volume compensator mechanism could be made from otherelements, such as a disk, piston, vane, plunger, slide, closed cellfoam, bellow, or the like.

In the present exemplary embodiment, diaphragm element 120 is attachedto bulb base 110 to create a substantially impermeable seal. Forexample, the perimeter of diaphragm element 120 may be clamped to aflange or seat feature of the bulb base 110. As shown in FIG. 1,diaphragm element 120 includes a sealing bead 122 to improve sealingcharacteristics. While FIG. 1 depicts one possible sealingconfiguration, one skilled in the art would recognize that other sealingtechniques could be used.

In FIG. 1, diaphragm element 120 is attached to bulb base 110 to allowdiaphragm element 120 to function as a liquid-volume compensatormechanism. For example, as LEDs 103 produce heat, the thermallyconductive liquid 111 expands, increasing the pressure inside theenclosed volume defined between shell 101 and bulb base 110. As shown inFIG. 1, at least a portion of one surface of diaphragm element 120 is influidic connection to the thermally conductive liquid 111 such that theliquid pressure exerts a force on at least part of diaphragm element120. Diaphragm element 120 is able to deflect from a first position to asecond position, in response to the increase in liquid pressureresulting from the volume of the thermally conductive fluid expandingfrom a first volume to a second volume.

The size and shape of diaphragm element 120 are selected to provide aliquid-volume compensator mechanism with an expandable volume (V_(e)).The size of the expandable volume (V_(e)) depends on several parameters,including total liquid volume (V_(f)), the lowest average fluidtemperature (T_(a)), highest average bulb temperature (T_(b)), andcoefficient of thermal expansion (α). The minimum capacity of theexpandable volume (V_(e(min))) can be calculated as:

V _(e(min)) =V _(f)×α(T _(b) −T _(a)).   (Equation 1)

V_(f) is the total liquid volume at the lowest average fluid temperature(T_(a)) that is approximately the volume of thermally conductive liquid111 as installed in the LED bulb 100 during manufacturing. Exemplaryranges for V_(f) at 25° C. include a range of 15 to 90 ml and apreferred range of 40 to 60 ml. α is the coefficient of thermalexpansion, which is a material property of the thermally conductiveliquid 111. α can be selected to minimize or reduce the expandablevolume (V_(e)). An exemplary range of α includes 1.3×10⁻³° C.⁻¹ to8×10⁻⁴° C.⁻¹.

T_(a) and T_(b) are based on estimated environmental conditions andmaximum operating temperature of the LEDs 103. Using Equation 1 tocalculate V_(e) of the liquid-volume compensator mechanism, the lowestexpected T_(a) should be used. An exemplary range for T_(a) includes−40° C. to +40° C. T_(b) is the average, steady-state temperature of thethermally conductive liquid 111 when the LED bulb 100 is operating atfull power. An exemplary T_(b) is approximately 90° C. Preferably, T_(b)should be below 120° C. The LED bulb can reach steady-state temperatureafter 180 minutes of continuous operation.

In the present exemplary embodiment, the liquid-volume compensatormechanism (e.g., diaphragm element 120) provides a V_(e) that isslightly larger than V_(e(min)) calculated using Equation 1. Anexemplary V_(e) of the liquid-volume compensator mechanism is at least 5ml. Another exemplary V_(e) of the liquid-volume compensator mechanismis at least 7 ml.

As shown in FIG. 1, in the present exemplary embodiment, an opening isprovided at the center of the LEDs 103 so that thermally conductiveliquid 111 is in fluidic connection with at least a portion of diaphragmelement 120. A relatively smaller opening has the advantage of reducingthe amount of light absorbed by diaphragm element 120. For example, theopening can be less than 5 mm but larger than 1 mm in diameter. Toreduce the light absorbed by diaphragm element 120, the opening may becovered with a perforated plate or screen. The opening can also becovered with a reflective baffle.

As noted above, light bulbs typically conform to a standard form factor,which allows bulb interchangeability between different lighting fixturesand appliances. Accordingly, in the present exemplary embodiment, LEDbulb 100 includes connector base 115 for connecting the bulb to alighting fixture. In one example, connector base 115 may be aconventional light bulb base having threads 117 for insertion into aconventional light socket. However, as noted above, it should beappreciated that connector base 115 may be any type of connector formounting LED bulb 100 or coupling to a power source. For example,connector base may provide mounting via a screw-in base, a dual-prongconnector, a standard two- or three-prong wall outlet plug, bayonetbase, Edison Screw base, single pin base, multiple pin base, recessedbase, flanged base, grooved base, side base, or the like.

FIG. 2A depicts a cross-sectional view of LED bulb 200 with an array ofLEDs 103 that are mounted in an outward orientation to improve lightdistribution. As shown in FIG. 2A, the LEDs 103 are also directed awayfrom the liquid-volume compensator mechanism, reducing shadows or darkregions created by exposed portions of the liquid-volume compensatormechanism. FIG. 2A depicts a centrally located liquid-volume compensatormechanism including a diaphragm element 120 attached to piston 222 andcap 224 using guide rod 226 as a threaded fastener. In the presentexemplary embodiment, diaphragm element 120 is clamped between piston222 and cap 224 to create a substantially impermeable seal. Theperimeter of diaphragm element 120 may also be clamped to bulb base 110to create a substantially impermeable seal.

As described above, LEDs 103 produce heat, and the thermally conductiveliquid 111 expands, increasing the pressure inside the enclosed volumecreated between shell 101 and bulb base 110. The liquid-volumecompensator mechanism is exposed to the thermally conductive liquid 111so that the liquid pressure exerts a force on one or more of the partsof the liquid-volume compensator mechanism. In the embodiment depictedin FIG. 2A, the liquid pressure exerts a force on the diaphragm element120 and cap 224.

The liquid-volume compensator mechanism is able to deflect or deform inresponse to the increase in pressure resulting in an increased volume.In FIG. 2A, the sidewall of diaphragm element 120 is able to roll orfold as diaphragm element 120 is deflected. Sufficient clearance isprovided between bulb base 110 and piston 222 to allow the sidewall ofdiaphragm element 120 to fold or roll. Diaphragm element 120 can havesidewalls that are tapered or crowned. Diaphragm element 120 can alsohave sidewalls that are substantially cylindrical.

FIG. 2A depicts a liquid-volume compensator mechanism (e.g., diaphragmelement 120, piston 222, cap 224, and guide rod 226) in an extendedposition. FIG. 2B depicts LED bulb 200 with the liquid-volumecompensator mechanism in a retracted position. The liquid-volumecompensator mechanism moves between an extended position and a retractedposition to provide an increase in liquid volume capacity of the LEDbulb 200 due to thermal expansion of thermally conductive liquid 111.For example, the extended position may represent the position of theliquid-volume compensator mechanism when the thermally conductive liquid111 is cool (e.g., bulb is not in operation). The retracted position mayrepresent the position of the liquid-volume compensator mechanism whenthe thermally conductive liquid 111 is warm (e.g., bulb is in operationand has reached a steady-state temperature).

In FIG. 2A, piston 222 provides support for diaphragm element 120 toprevent collapse or buckling of the diaphragm walls. Piston 222 can alsoinclude piston sidewalls that are at least as long as the sidewalls ofdiaphragm element 120. Guide rod 226 slides through guide bore 230 toallow axial movement of the diaphragm element 120, piston 222, and cap224. Guide rod 226 may be made of stainless steel, brass, bronze,aluminum, or the like. In the present exemplary embodiment, guide rod226 and guide bore 230 are of different materials to prevent galling orseizure. Alternatively, guide bore 230 is a sleeve or insert made of amaterial that is different from the material of bulb base 110.

FIG. 3A depicts a cross-sectional view of LED bulb 300, including aliquid-volume compensator mechanism with a spring-loaded piston toprovide a positive pressure in thermally conductive liquid 111. Apositive pressure can be maintained inside the bulb to improve theliquid-to-air seal between shell 101 and bulb base 110. By maintaining apositive pressure in the thermally conductive liquid 111, the sealprovides a liquid-impermeable barrier, preventing the liquid fromleaking out. However, it is not necessary that the seal beair-impermeable, as the positive liquid pressure prevents air from beingdrawn into LED bulb 300 (e.g., by vacuum). In general, providing aliquid-impermeable seal is more practical and cost-effective thanproviding an air-impermeable seal. Thus, an LED bulb with a pressurized,thermally conductive liquid 111 offers improved sealing characteristics.

Return spring 310 may also be selected to provide a force that issufficient to overcome friction in the liquid-volume compensatormechanism. For example, a positive force may be required to restore theshape of diaphragm element 120 corresponding to an extended position ofthe liquid-volume compensator mechanism. Return spring 310 can beselected so that a maximum liquid pressure is not exceeded when returnspring 310 is compressed.

In FIG. 3A, the liquid-volume compensator mechanism includes a diaphragmelement 120 attached to piston 222 (FIG. 2A) and cap 224 using guide rod226 (FIG. 2A) as a threaded fastener. As shown in FIG. 3A, return spring310 is a wound compression spring mounted between piston 222 (FIG. 2A)and a flange or seat in bulb base 110. A sealed air chamber in bulb base110 may be provided to provide a return force. In some embodiments, anextension spring, torsional spring, polymer spring, or the like is usedto provide a return force.

FIG. 3A depicts the liquid-volume compensator mechanism in an extendedposition. FIG. 3B depicts LED bulb 300 with the liquid-volumecompensator mechanism in a retracted position. As depicted in FIG. 3B,in the retracted position, return spring 310 is compressed.

FIG. 4A depicts a cross-sectional view of an exemplary LED bulb 400 witha center protrusion 420 for shrouding the liquid-volume compensatormechanism. By shrouding the liquid-volume compensator mechanism,protrusion 420 prevents the mechanism from interfering with lightdistribution. For example, protrusion 420 may have a surface finish toreduce the amount of light absorbed by the protrusion 420. Consequently,protrusion 420 will absorb less light than would an unshrouded orexposed liquid-volume compensator mechanism. Also, it is advantageousthat the center protrusion be located in LED bulb 400 so that it doesnot block light emitted from LEDs 103.

By shrouding the liquid-volume compensator mechanism, protrusion 420prevents the mechanism from interfering with convective liquid flowwithin the LED bulb 400. Consequently, the outside surface of protrusion420 facilitates convective flow of thermally conductive liquid 111.Protrusion 420 may also include tapered and rounded corners such thatcurrents in the thermally conductive liquid 111 are able to follow apassive convective flow. The shape of protrusion 420 should minimizestagnant or dead zones in the convective flow of thermally conductiveliquid 111. For example, protrusion 420 can be shaped to facilitateconvection of thermally conductive liquid 111 when LED bulb 400 is indifferent orientations.

Protrusion 420 may also facilitate heat conduction into thermallyconductive liquid 111 by providing additional surface area. Heatproduced by LEDs 103 is conducted through LED mount 107 to protrusion420, and then conducted from protrusion 420 to thermally conductiveliquid 111.

In the present embodiment, LED mount 107 includes the protrusion 420 topartially enclose cavity 422 containing the liquid-volume compensatormechanism. The liquid-volume compensator mechanism depicted in FIG. 4Aincludes diaphragm element 120, piston 222, cap 224, guide rod 226, andreturn spring 310. As shown in FIG. 4A, one end of guide rod 226 extendstoward the shell. The center protrusion 420 includes guide bore 230allowing the liquid-volume compensator mechanism to move in an axialdirection. By orienting the guide rod 226 toward the shell, theliquid-volume compensator mechanism can be partially located in theenclosed volume of LED bulb 400 without creating a large obstruction.Placing the liquid-volume compensator mechanism partially within theenclosed volume allows the size of the bulb base to be reduced.

As shown in FIG. 4A, protrusion 420 and LED mount 107 are made from thesame part. However, protrusion 420 may be a separate part or may be madefrom the same part as the bulb base. Protrusion 420 may include one ormore liquid paths to allow flow of thermally conductive liquid 111 intoand out of cavity 422.

In FIG. 4A, as the LEDs 103 generate heat, the thermally conductiveliquid 111 exerts a force on the end of guide rod 226, which isconnected to diaphragm element 120 via piston 222 and cap 224. Thermallyconductive liquid 111 can also exert a force on other parts that areattached to diaphragm element 120, such as piston 222 and cap 224.

Diaphragm element 120 is able to deflect or deform in response to theincrease in pressure resulting in an increased volume. In FIG. 4A, thesidewall of diaphragm element 120 is able to roll or fold as diaphragmelement 120 is deflected. Sufficient clearance is provided betweencavity 422 and piston 222 to allow diaphragm element 120 to fold orroll.

FIG. 4A depicts the liquid-volume compensator mechanism in an extendedposition. FIG. 4B depicts LED bulb 400 with the liquid-volumecompensator mechanism in a retracted position. As depicted in FIG. 4B,in the retracted position, return spring 310 is compressed.

In FIG. 4A, LED bulb 400 also includes a feature for limiting the inwardstroke of the liquid-volume compensator mechanism. For example,protrusion 420 may include a stroke-limiting feature, such as a seat orflange that prevents cap 224 from moving past an extension position. Inembodiments that include return spring 310, a stroke-limiting feature isdesirable to prevent the sidewalls of diaphragm element 120 from beingloaded by the return force. Thus, in one exemplary embodiment, thestroke of the diaphragm element 120 should be slightly larger than whatis allowed by the stroke-limiting feature.

FIG. 5A depicts a cross-sectional view of an exemplary LED bulb 500 withcenter protrusion 420 and a liquid-volume compensator mechanism. Theliquid-volume compensator mechanism depicted in FIG. 5A includesdiaphragm element 120, piston 222, cap 224, and guide rod 226. In theembodiment depicted in FIG. 5A, a sealed air chamber in bulb base 110may be provided to provide a return force such that the piston workswithout a return spring. In this embodiment, the piston retracts as thefluid expands with heat and extends as the fluid contracts as it cools.FIG. 5A depicts the liquid-volume compensator mechanism in an extendedposition. FIG. 5B depicts LED bulb 500 with the liquid-volumecompensator mechanism in a retracted position.

The diameter and stroke of the liquid-volume compensator mechanism areconfigured to reduce the size of the bulb base. For, example, thediameter of the liquid-volume compensator mechanism is reduced and thestroke increased to provide a narrower bulb base. Also, a thermallyconductive liquid with a reduced thermal expansion can be selected,allowing for a reduction in the expandable volume capacity and the sizeof the liquid-volume compensator mechanism.

Although a feature may appear to be described in connection with aparticular embodiment, one skilled in the art would recognize thatvarious features of the described embodiments may be combined. Moreover,aspects described in connection with an embodiment may stand alone.

1-20. (canceled)
 21. A light-emitting diode (LED) bulb comprising: ashell; one or more LEDs disposed within the shell; a thermallyconductive liquid held within the shell, wherein at least a portion ofthe thermally conductive liquid is in contact with the shell; a centralprotrusion disposed within a central portion of the shell; and aliquid-volume compensator mechanism disposed, at least partially, withinthe central protrusion, wherein the central protrusion includes anopening configured to fluidically connect the liquid-volume compensatormechanism to the thermally conductive liquid, and wherein theliquid-volume compensator mechanism is configured to compensate forexpansion of the thermally conductive liquid.
 22. The LED bulb of claim21, wherein the central protrusion is configured to reduce lightabsorption.
 23. The LED bulb of claim 21, wherein the central protrusionis disposed within the central portion of the shell to not block lightemitted by the one or more LEDs.
 24. The LED bulb of claim 21, whereinthe central protrusion is configured to facilitate convective flow ofthe thermally conductive liquid.
 25. The LED bulb of claim 24, whereinthe central protrusion includes tapered and rounded corners.
 26. The LEDbulb of claim 21, wherein the central protrusion is shaped to facilitateconvection of the thermally conductive liquid when the LED bulb is indifferent orientations.
 27. The LED bulb of claim 21, wherein thecentral protrusion is configured to facilitate heat conduction into thethermally conductive liquid.
 28. The LED bulb of claim 21, wherein theliquid-volume compensator mechanism comprises a flexible diaphragm. 29.The LED bulb of claim 28, wherein at least a portion of one surface ofthe flexible diaphragm is in fluidic connection with the thermallyconductive liquid, and wherein liquid pressure resulting from theexpansion of the thermally conductive liquid exerts a force on theportion of the surface of the flexible diaphragm to deflect the flexiblediaphragm from a first position to a second position.
 30. The LED bulbof claim 28, further comprising: a base connected to the shell; and anenclosed cavity defined, at least in part, within the base, the enclosedcavity containing the flexible diaphragm.
 31. The LED bulb of claim 28,further comprising: a spring element configured to apply a return forceon one face of the flexible diaphragm.
 32. The LED bulb of claim 28,further comprising: a sealed air chamber configured to provide a returnforce on one face of the flexible diaphragm.
 33. The LED bulb of claim28, wherein the flexible diaphragm is configured to provide a positivepressure in the thermally conductive liquid.
 34. The LED bulb of claim21, wherein the liquid-volume compensator mechanism comprises a bellow.35. The LED bulb of claim 21, further comprising a base, wherein thethermally conductive liquid fills a volume defined within the shell andbase, and wherein the volume includes less than about 5 percent of agas.
 36. The LED bulb of claim 35, wherein the volume contains between15 and 90 milliliters of thermally conductive liquid.
 37. The LED bulbof claim 21, wherein the thermally conductive liquid has a rate ofthermal expansion between 1.3×10−3° and 8×10−4° Celsius−1.
 38. The LEDbulb of claim 21, wherein the thermally conductive liquid is siliconeoil.
 39. The LED bulb of claim 21, further comprising: an LED mountdisposed within the shell, wherein the one or more LEDs are mounted onthe LED mount.
 40. The LED bulb of claim 39, wherein the one or moreLEDs are positioned toward the vertical middle of the shell, when theLED bulb is in a vertical orientation.
 41. The LED bulb of claim 40,wherein the one or more LEDs comprise a plurality of LEDs.
 42. The LEDbulb of claim 41, wherein the LEDs are disposed in a radial pattern,with each LED facing a different radial direction.
 43. The LED bulb ofclaim 39, wherein the one or more LEDs are oriented at an angle that isnon-vertical and non-horizontal, when the LED bulb is in a verticalorientation.
 44. The LED bulb of claim 21, further comprising a base,wherein the base comprises a connector base configured to connect theLED bulb to a lighting fixture.
 45. A light-emitting diode (LED) bulbcomprising: a base; a shell connected to the base; one or more LEDsdisposed within the shell; a thermally conductive liquid held within theshell, wherein at least a portion of the thermally conductive liquid isin contact with the shell; a central protrusion disposed within theshell; and a liquid-volume compensator mechanism disposed, at leastpartially, within the central protrusion, wherein the central protrusionincludes an opening configured to fluidically connect the liquid-volumecompensator mechanism to the thermally conductive liquid, and whereinthe liquid-volume compensator mechanism is configured to compensate forexpansion of the thermally conductive liquid.
 46. The LED bulb of claim45, wherein the central protrusion is disposed within the centralportion of the shell to not block light emitted by the one or more LEDs.47. The LED bulb of claim 45, wherein the central protrusion isconfigured to facilitate convective flow of the thermally conductiveliquid.
 48. The LED bulb of claim 45, wherein the central protrusion isshaped to facilitate convection of the thermally conductive liquid whenthe LED bulb is in different orientations.
 49. The LED bulb of claim 45,wherein the central protrusion is configured to facilitate heatconduction into the thermally conductive liquid.
 50. The LED bulb ofclaim 45, wherein the liquid-volume compensator mechanism comprises aflexible diaphragm.
 51. The LED bulb of claim 45, wherein theliquid-volume compensator mechanism comprises a bellow.
 52. The LED bulbof claim 45, wherein the thermally conductive liquid fills a volumedefined within the shell and base, and wherein the volume includes lessthan about 5 percent of a gas.
 53. The LED bulb of claim 52, wherein thevolume contains between 15 and 90 milliliters of thermally conductiveliquid.
 54. The LED bulb of claim 45, wherein the thermally conductiveliquid has a rate of thermal expansion between 1.3×10−3° and 8×10−4°Celsius−1.
 55. The LED bulb of claim 45, wherein the thermallyconductive liquid is silicone oil.
 56. The LED bulb of claim 45, furthercomprising: an LED mount disposed within the shell, wherein the one ormore LEDs are mounted on the LED mount.
 57. The LED bulb of claim 56,wherein the one or more LEDs are positioned toward the vertical middleof the shell, when the LED bulb is in a vertical orientation.
 58. TheLED bulb of claim 57, wherein the one or more LEDs comprise a pluralityof LEDs.
 59. The LED bulb of claim 58, wherein the LEDs are disposed ina radial pattern, with each LED facing a different radial direction. 60.The LED bulb of claim 56, wherein the one or more LEDs are oriented atan angle that is non-vertical and non-horizontal, when the LED bulb isin a vertical orientation.
 61. A method of making a light-emitting diode(LED) bulb, the method comprising: connecting a shell to a base;disposing one or more LEDs within the shell; disposing a centralprotrusion within the shell; disposing a liquid-volume compensatormechanism, at least partially, within the central protrusion; andfilling the shell with a thermally conductive liquid, wherein at least aportion of the thermally conductive liquid is in contact with the shell,wherein the central protrusion includes an opening configured tofluidically connect the liquid-volume compensator mechanism to thethermally conductive liquid, and wherein the liquid-volume compensatormechanism is configured to compensate for expansion of the thermallyconductive liquid.
 62. The method of claim 61, wherein the centralprotrusion is disposed within the central portion of the shell to notblock light emitted by the one or more LEDs.
 63. The method of claim 61,wherein the liquid-volume compensator mechanism comprises a flexiblediaphragm, and wherein at least a portion of one surface of the flexiblediaphragm is in fluidic connection to the thermally conductive liquid.